There are many neurological procedures which require the accurate placement of a neurological instrument, including for biopsy, radioactive seed placement, and lesion generation. One of the most common neurological procedures requiring accurate placement is a ventriculostomy procedure in which a cerebral ventricle drain or shunt is installed. Such a drain or shunt is utilized for ventricular drainage when a patient manifests hydrocephalus resulting from congenital brain malformations, acute or chronic infections, tumors, intraventricular hemorrhage, or normal pressure hydrocephalus.
Conventional procedures for the placement of ventricular drains or shunts rely heavily on the skill of the neurosurgeon, and/or are relatively expensive and time consuming. After a CT scan, or other imaging, the neurosurgeon forms a burr hole in the skull, and then the neurosurgeon guides a catheter through the burr hole toward landmarks on the opposite side of the patient's head. It is necessary that the neurosurgeon be able to completely accurately visualize the internal tomography of the brain when performing this procedure, and it is presumed that the catheter is properly located when the surgeon obtains fluid returned through the catheter. In some circumstances, the neurosurgeon feels it advisable to check the location of the catheter, and for that purpose the patient must be subjected to another CT scan of the brain in order to verify proper location of the catheter. Since each separate, individual, CT scan is expensive, and since the prior art procedures are time consuming both for the neurosurgeon and the anaesthesiologist, there has long been a need for procedures more regularly and inexpensively accurately placing ventricular drain or shunt catheters, which will result in longer shunt patency and decreased morbidity due to shunt malposition.
According to one aspect of the invention of the parent application, a stereotactic neurological instrument placement guide is provided that may be utilized in numerous different types of neurological procedures, and which has ideal suitability for use in ventriculostomy procedures. The guide according to the invention is simple to construct and to utilize, and can readily enhance accuracy, reduce time, increase confidence, and reduce cost for a given level of confidence, in ventriculostomy procedures and other neurological treatment methods.
The stereotactic guide of the parent application has only first and second skull engaging point members, which have a common central axis. A frame mounts the skull engaging point members for controlled movement with respect to each other along the central axis. Means are provided defining a linear guide passage in the first point member, a straight line extension of the linear guide passage extending along a common central axis, and the linear guide passage is large enough for the passage of a neurological instrument (e.g. catheter or shunt) through it. The termination of the first point member coaxial with the linear passageway and common central axis provides for stabilizing the first point member in a burr hole; for example the termination may comprise a truncated cone.
The point members may be attached to arms, which in turn are attached to a guide sleeve and a guide element (bar or rod) which are movable with respect to each other. A locking screw can lock them in a position to which they have been moved, or they may be biased toward each other by an elastic band, spring loading, or the like. The means defining a linear passage may comprise a slotted sleeve rigidly fixed to the frame arm, with a slotted tubular element received within the sleeve and rotatable from one position in which the slots of the sleeve and tubular member are not aligned, to a second position in which the slots are aligned. When the slots are not aligned, the guide passage is closed and provides positive guiding of the catheter therethrough. When the slots are aligned, the placement guide may be removed from contact with the patient's skull, and the catheter.
According to the parent application, the key to proper utilization of the stereotactic neurological instrument placement guide is the proper location of the fixing point on the opposite side of the patient's skull from the burr hole. The positive location of the fixing point, which will receive the second point member of the placement guide, opposite the proposed site for the burr hole is determined utilizing a CT scan, magnetic resonance imaging (MRI), or another type of coordinate multiplanar tomographic imaging of the patient's skull. Utilizing X, Y, and Z coordinates for the burr hole (marked by a nipple marker or the like), and determining the coordinates of the particular portion of the ventricle, or other location within the brain, desired to be acted upon by the neurosurgeon, the data from the imaging can be used to calculate the loci of points along a straight line between the burr hole and the target area, which loci can be extended to the patient's skull on the opposite side thereof from the burr hole, and that part of the patient's skull can be marked with a nipple marker, oil, or the like. The calculations are preferably provided by vector parameterization, utilizing a programmable scientific calculator, and the gantry angle of the imaging equipment can be automatically accommodated.
Desirably the distance of the target point from the burr hole is also calculated according to the invention, so that the neurosurgeon can use indicia on the catheter to determine when the catheter has been inserted the distance necessary to properly position it at the target. Practicing the method according to the invention, since the placement of the fixing point is accurately determined, there is no necessity for a second CT scan, or the like.
While the invention will be described herein primarily with respect to ventriculostomy procedures, it is to be understood that both the apparatus and procedures according to the invention may be applied to a wide variety of neurological practices. In fact, the basic positioning facilitating features of the parent application are applicable not just to neurosurgery, but in general to determining the position of a line between two points on or within a human patient's body utilizing data normally determined from a coordinate multiplanar tomographic imaging (CT, MRI, etc.) of the patient's body during which the patient is disposed at an angle, and is incrementally advanced between images. Utilizing the present invention it is possible to practice procedures not heretofore contemplated, or to maximize the accuracy of present procedures, since according to the invention it is possible to accurately locate and determine the coordinates of two or more points on or within a human body (e.g. within the brain).
Also according to the present invention, the utility of the stereotactic neurological instrument placement guide described above is improved by utilization of a cerebral instrument guide frame and supporting computer programs. The cerebral instrument guide frame, and related procedures, according to the invention allow the neurosurgeon to mark the burr hole site and fixing point on the patient in the operating suite prior to applying the stereotactic instrument guide described above. This eliminates the need to mark these sites on the patient in the multiplanar tomographic imaging (CT scanning) suite. In this way it is possible to avoid accidental erasure or movement of identifying marks or markers placed by the radiologist. Further, instead of having a mark on the scalp, the neurosurgeon can directly mark the patient's skull, improving accuracy of the stereotactic instrument guide described above.
The cerebral instrument guide frame according to the present invention is preferably mounted in the patient's ears and on the bridge of the patient's nose. In addition to allowing--in association with the computer programs described hereafter--accurate location of the burr hole and fixing point, the cerebral instrument guide frame can serve as a fixing point for the stereotactic instrument guide described earlier. The cerebral instrument guide frame according to the invention thus provides a neurosurgeon a simple stereotactic method for catheter placement, or for other neurological procedures, and expands the utility of the stereotactic instrument guide described above.
A cerebral instrument guide frame for use with a live human patient according to the present invention comprises the following elements: A first arcuate member having first and second ends, and a radius. A second arcuate member having first and second ends and a radius, (the radius of the second arcuate member being greater than the radius of the first arcuate member). Aligned first and second openings provided adjacent each of the first and second ends of each of the first and second arcuate members. First and second rigid ear fixator rods mounted in the aligned openings, the first in the openings adjacent the first ends of the first and second arcuate members, and the second in the openings adjacent the second ends of the first and second arcuate members, the rods mounted for movement with respect to the first and second arcuate members along a common axis passing through the openings, and the arcuate members mounted for pivotal movement with respect to each other about the common axis. An abutment mounted on one of the arcuate members for engaging a portion of a patient's head to preclude movement of the arcuate member past that portion of the patient's head. And an instrument guide mounted on the other of the arcuate members for guiding an instrument aligned therewith into contact with the patient's head, the guide directed to the midpoint of the common axis.
The abutment preferably comprises a nasal bridge fixation element for engaging the bridge of a patient's nose, and the instrument guide comprises a tubular element mounted to one of the arcuate elements for movement with respect to that element along the arcuate extent thereof. The abutment is mounted on the first arcuate element and the instrument guide on the second arcuate element. A pair of orbit pads also may be mounted on the first arcuate element on opposite sides of the nasal bridge fixation element for engaging the patient's orbits. The tubular instrument guide element has an internal diameter slightly greater than the external diameter of a needle. The first and second arcuate members each preferably comprise a hemicircle, or semicircle, and the nasal bridge fixation element is mounted for radial movement with respect to the first arcuate element (that is, along the radius thereof). The first and second arcuate members preferably are made of aluminum, a rigid durable sterilizable medical-grade structural plastic, or the like.
The cerebral instrument guide frame according to the invention may be used in combination with the stereotactic neurological instrument placement guide as described above, with one of the point members of the skull engaging elements of the stereotactic neurological instrument guide engaging the tubular instrument guide element, and in alignment therewith. When the guide frame according to the present invention is combined with the stereotactic neurological instrument placement guide described above, typically the second point member comprises the "one of the point members", and the first and second arcuate members make an angle of about 160.degree.-180.degree. with respect to each other with the second point member in alignment with the tubular instrument guide element.
According to another aspect of the present invention, a cerebral instrument guide for use with a live human patient is provided which comprises the following elements: A first frame element having first and second ends, and a central portion. A nasal bridge fixation mounted on the first frame element at the central portion, and movable with respect to the first frame element. A second frame element having first and second ends, and a central portion. Pivot means for mounting the first and second frame elements for pivotal movement with respect to each other about a common axis. An instrument guide mounted on the second frame element, and movable with respect thereto and directed toward the midpoint of the common axis. And means for positively locating the pivot means with respect to the patient's head so that the axis remains stationary with respect to a predetermined portion of the patient's head.
Typically, the pivot means and the positively locating means comprise first and second ear fixation rods adapted to be inserted into the patient's ears and received within aligned openings in the first and second ends of the first and second frame elements. The rods may be slidable with respect to the frame elements to move toward and away from the patient's ears. The frame elements preferably comprise first and second hemicircles with the second frame element hemicircle having a larger radius than the first element hemicircle. The ear rods preferably have some covers--where they engage the patient's ears--of a soft material, such as soft rubber, to allow seating of the rod ends into the external auditory meatia.
The computer program utilized with the present invention accepts data from computed tomographic images representing five separate points: a target point in a cerebral ventricle, a point representing the intended burr hole site on the skull, a point at the right external auditory meatus, a point at the left external auditory meatus, and a point representing the interior superior edge of either bony orbit. The program corrects for CT scanner gantry tilt and then calculates an angle at which to separate and set the first and second arcs of the cerebral instrument guide frame, and an angle between a line containing the midpoint of the line in space (the common axis of the arcuate members) and the skull point, and a line in space connecting the ends of the arcs. The sliding instrument guide mounted on the second arcuate member is set at this calculated angle, and directed toward the skull.
When the apparatus described above is utilized, the patient first has a CT scan (or other multiplanar tomographic imaging) of the brain and skull. Neither the cerebral instrument guide frame nor the stereotactic instrument guide is mounted on the patient's head during the acquisition of the CT data, but following the CT scan procedure, the target, burr hole, right and left auditory meatia, and orbital ridge points are entered into the computer program to calculate the angles necessary. In the operating room, with or without the patient under general anesthesia, the cerebral instrument guide frame is then applied to the patient's head by symmetrically advancing the rods connecting the arc centrally toward and into the external ear canals, and then by seating the mid-line U-shaped nasal bridge onto the nasion. The angle between the first and second arcuate members and the position of sliding guide along the first arc are set, and the neurosurgeon can then pass a long needle down the sliding guide through the scalp and onto the skull at the skull point where a distinguishing mark for the burr hole can be made, and later for the fixing point. The cerebral instrument guide frame may then be removed and the stereotactic instrument guide used as a described above, or the cerebral instrument guide frame can be left in placed and repositioned to accept the fixing point of the stereotactic instrument guide.
According to another aspect of the present invention, a method of positively locating a burr hole site on a patient's skull during a neurological procedure on a human patient, using a guide comprising first and second frame members mounted for pivotal movement with respect to each other about a common axis defined by ear fixators, one of the frame members having a nasal bridge fixation, and the other having an instrument guide, is provided. The method comprises the steps of: (a) Effecting coordinate multiplanar tomographic imaging of the patient's head. (b) During the practice of step (a) determining locations of the target in the patient's head, the burr hole site on the patient's skull, the patient's left and rights auditory medati, and at least one of the patient's orbital ridges. (c) With a computer, calculating from the data determined in step (b) the angular positions of the frame members of the guide to mark the burr hole site and fixing point on the patient's skull, and the proper position of the instrument guide along the second frame member. Then (d) moving the ear fixations of the guide into positive contact with the patient's ears, and the nasal bridge fixation into positive contact with the patient's nasal bridge. And (e) moving the second frame member of the guide frame with respect to the first frame member to have the proper orientation to mark the burr hole site, and moving the instrument guide to the proper position along the second frame member, and then marking the burr hole site using the instrument guide.
The method can also be for positively locating a fixing point on the patient's skull in which case there is the further step of (f) moving the second frame member of the guide with respect to the first frame member to have the proper orientation to mark the fixing point on the patient's skull, and then marking the fixing point site using the instrument guide. Also, there may be the still further step, with the guide in place with the relative positions of the components as provided in step (f), of moving a stereotactic neurological placement guide having end point members into operative association with the burr hole site and the instrument guide on the second frame member; effecting formation of a burr hole; and passing an instrument through one of said stereotactic neurological placement guide point members engaging said burr hole, to pass the instrument to the target within the patient's skull.
Alternatively, the guide is removed from the patient's ears and nose, a burr hole is formed at the burr hole site, and the end point members of a stereotactic neurological placement guide having end point members is moved into operative association with the burr hole site and a fixing site opposite the burr hole site on the patient's skull. The neurlogical instrument is inserted through the burr hole and placement guide into operative association with the target within the patient's skull.
Step (c) may be practiced in part by using vector parameterization, and step (a) is practiced using a non-zero angle of inclination between imaging equipment and the patient while there is an incremental advance between images, the computations in step (c) taking into account the angle of inclination and the increment of advance between images.
In general, the invention facilitates and provides a method of performing a neurological procedure on a human patient utilizing a scanner, a cerebral instrument guide frame, and an operating room, that is greatly simplified with respect to the prior art, allowing the scanning to be done without a frame on the patient's head, and avoiding the expense and time delay of moving a patient from the operating room back to the scanner, and running a second scan on the patient with a frame attached to the patient's head. This aspect of the method of the invention comprises the steps of substantially sequentially: (a) Effecting coordinate multiplanar tomographic imaging of the patient's head with the scanner while the patient's head is free of frame attachments, to obtain data necessary for performing a neurological procedure. (b) Moving the patient to the operating room. (c) In the operating room, utilizing the data from step (a), fixing the cerebral instrument guide frame on the patient's head; and (d) substantially immediately after step (c), in the operating room, without transporting the patient back to the scanner to effect a second imaging, performing the neurological procedure on the patient, utilizing the cerebral instrument guide frame to guide one or more medical instruments (e. g. catheter, light pipe, laser, etc.).
It is a primary object of the present invention to provide an accurate, effective, and simplified manner of performing neurlogical procedures on a human patient. This and other objects of the invention will become clear from an inspection of the detailed description of the invention and from the appended claims.